Originally Posted by Armageddon

Excuse me if I misinterpreted your question at all. Our knock sensor location and frequencies were posted above but I read your question like you wanted to know how it actually detected knock? Knock sensors are Piezoelectric sensors. The Piezoelectric effect is an example of how energy is converted from one form to another, "mechanical to electrical." A knock sensor is made up of a polarized crystal encased in a sturdy conductive principle. When a polarized crystal is compressed it forms a voltage through mechanical deformation. The conductive principle directs the newly aquired AC current to the computer. First it has to go through a DC converter so the computer can read it. The harder the knock, the more the crystal is compressed, which determines the amount of voltage sent to the computer. The higher the voltage the more drastic measures the computer takes to correct the situation.